The Lachlan Transverse Zone is a major yet subtle west-northwest-trending s
tructure that cuts across the Tasmanides of southeastern Australia. It exte
nds from the western part of the Olepoloko Fault in the west, where it mark
s the boundary between the Delamerian and Thomson Orogens, across the Lachl
an Orogen into the Sydney Basin where it is represented by dykes and intrus
ions. The western part of the Lachlan Transverse Zone is defined by west-no
rthwest-trending faults. In the Eastern Belt of the Lachlan Orogen, it is d
efined as a corridor of west-northwest-trending folds and faults that disru
pt major folds and faults which constitute the regional grain of the orogen
. The Lachlan Transverse Zone was active in the development of the Lachlan
Orogen since at least the Middle Ordovician period. It has influenced the p
artitioning of upper crustal extensional and contractional deformation, the
intrusion of igneous bodies as well as the distribution of copper-gold dep
osits in the Eastern Belt of the orogen. The Lachlan Transverse Zone appear
s to be an extension of the Proterozoic Amadeus Transverse Zone, as well as
an extension of a west-northwest-trending transform segment in the Tasman
Line that controlled the Neoproterozoic and Cambrian breakup of cratonic Au
stralia. For these reasons, we suggest that the Lachlan Transverse Zone rep
resents the reactivation of a fundamental crustal weakness in the cratonic
lithosphere that propagated into younger Neoproterozoic to Palaeozoic litho
sphere of oceanic and continental character.